1. Field of the Invention
The present invention relates to a heat exchanger for making heat exchange between high temperature fluid and low temperature fluid, and especially to a heat exchanger, which permits to provide economical effects and has a high reliability and safety.
2. Description of the Related Art
In general, a heat exchanger is used as a heat/cooling device, an evaporator or a condenser in a plant of electric generation by temperature difference, steam power, chemistry, food engineering and the like, a refrigerator and a heat pump. Such a heat exchanger can make heat exchange between high temperature fluid and low temperature fluid for the purposes of heating, boiling, evaporating, cooling and condensing fluid.
The conventional heat exchanger may be classified into a shell and tube heat exchanger, a plate type heat exchanger, a spiral type heat exchanger and the like. The plate type heat exchanger is generally used as an evaporator for boiling and evaporating a working fluid having a low temperature by heat of a high temperature fluid and as a condenser for absorbing heat through a low temperature fluid to condense a working fluid having a high temperature in a plant of electric generation by temperature difference, a refrigerator and a heat pump. An example of the conventional plate type heat exchanger used as the evaporator and the condenser is shown in FIGS. 6 and 7. FIG. 6 is an exploded perspective view illustrating essential components of the conventional heat exchanger. FIG. 7 is a schematic descriptive view of the conventional heat exchanger in an assembled condition.
The conventional plate type heat exchanger 100 as shown in FIGS. 6 and 7 is provided with plural pairs of plates 101, 102. In each pair, the plate 101 is placed on the other plate 102. Upper and lower guide rods 105, 106 held between a stationary frame 103 and a support rod 104 support the plural pairs of these plates 101, 102. The plural pairs of the plates 101, 102 are firmly held between the stationary frame 103 and a movable frame 107 that is mounted on the guide rods 105, 106. Two heat exchange passages A, B are formed on the opposite surfaces of each of the plates 101, 102. A heat-exchanger fluid 108 having a high or low temperature flows in the heat exchange passage A and a working fluid 109 flows in the other heat exchange passage B so as to make heat exchange.
The above-mentioned plates 101, 102 having a prescribed shape and a surface condition can be obtained by press-forming a plate-shaped material. Openings xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d, xe2x80x9ccxe2x80x9d and xe2x80x9cdxe2x80x9d through which the heat-exchanger fluid 108 or the working fluid 109 can pass, are formed at four corners of each of the plates 101, 102. Packing members 111, 112 are placed on the surfaces of the plates 101, 102, respectively, so as to prevent the heat-exchanger fluid 108 and the working fluid 109 from flowing in a mixing condition. The plates 101, 102 have the same shape, but the plates 102 is placed upside down relative to the normal placement of the plate 101.
However, in the conventional heat exchanger having the above-described structure, the heat exchange fluid 108 or the working fluid 109 supplied between the plates 101, 102 in the horizontal direction in FIG. 7 passes through the openings xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d, xe2x80x9ccxe2x80x9d and xe2x80x9cdxe2x80x9d and turns vertically so as to make a vertical flow between the plates 101, 102, thus flowing in a complicated manner and leading to a large pressure loss. Accordingly, it is necessary to increase a supplying pressure of each of the fluids. However, the fluid-tightness of the heat exchange passages A, B can not be obtained unless the packing members 111, 112 are firmly pressed against the plates 101, 102. In view of this fact, it is impossible to increase the pressure of the heat-exchanger fluid 108 or the working fluid 109 over the prescribed limit so as to prevent the leakage due to insufficient pressing of the packing members 111, 112. A number and size of the plates 101, 102 are also restricted, thus causing a problem. In addition, when ammonia or a mixture of ammonia and water is used as the working fluid 109, a sufficient safety cannot be obtained due to the use of the packing members 111, 112.
In order to solve the above-mentioned problems, there have conventionally been developed for practical use plate type heat exchangers as the products of ALFA RAVAL Co. Ltd., in which the plates that have been obtained by press-forming the material plate into a prescribed shape were joined with each other by a brazing method without using packing members to form an integral body, while forming heat exchange passages on the opposite surfaces of each plate, and there is no need for movable frame and stationary frame. However, a specific tool is required to join the plates with each other, leading to complicated manufacturing steps and requiring a high manufacturing cost.
When the conventional heat exchanger has a heat transferring face on which irregular portions are formed in order to improve the heat transferring effect and discharge fluid easily, which is produced through condensation, a remarkable pressure loss occurs. When the pressing accuracy for preparation of the plates 101, 102 is not so high, the plates 101, 102 come into contact with each other at their portions, which should not come into contact with each other, so that the pressing condition of the plates 101, 102 changes to impart an adverse influence to the close contact of the packing members 111, 112.
The ratio of area of the openings xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d, xe2x80x9ccxe2x80x9d and xe2x80x9cdxe2x80x9d to the plates 101, 102 is relatively high and these openings are formed by a removing process such as a punching step. Accordingly, a blanking process for the plates 101, 102 is carried out to form blanks having such waste portions. When the plates are to be used especially for the electric generation by temperature difference in seawater, they are formed of materials such as expensive titanium or special alloy in view of corrosion resistance, thus leading to occurrence of uneconomic problems in material costs. Japanese Patent Provisional Publication No. S60-80082 discloses the other plate type heat exchanger, in which the above-mentioned problems are taken into consideration. The other plate type heat exchanger has a structure in which a number of passage portions that are obtained by forming openings on the plates is limited to two on the upper and lower sides so as to solve the uneconomic problems in material costs and extremely increase the ratio of area of the heat transferring face to the plate. However, the other plate type heat exchanger has the passage portions, resulting in the occurrence of the uneconomic problems in costs of the material as used. In addition, the passage portions of the plate do not contribute to the heat exchange and it is therefore necessary to use the plate, which is larger than the essential area of the heat transferring face.
An object of the present invention, which was made in order to solve the above-described problems, is therefore to provide a heat exchanger in which the supporting structure of the heat transferring face is improved to permit the non-use of packing members and the release from the restriction due to the use of them, the heat transferring face has a simple shape to reduce the manufacturing cost and reliability and safety are improved.
In order to attain the aforementioned object, the heat exchanger of the present invention for making heat exchange between high temperature fluid and low temperature fluid, said apparatus comprises:
a shell having a box-shape, an inside of which is divided into at least three zones disposed in a prescribed direction by at least two parallel partition walls; and
a plurality of tubular heat transferring members, said heat transferring members comprising a plurality of tubular bodies each having opposite open ends and two surfaces being opposite in parallel to each other at a prescribed distance, said tubular bodies being disposed in parallel with each other in an intermediate zone of said zones of said shell, which locates between adjacent both zones different from said intermediate zone, so that a central axis of each of said tubular bodies coincide with a prescribed direction and said surfaces of said tubular bodies are opposite in parallel to each other, said tubular bodies passing through said at least two parallel partition walls so that the opposite open ends of each of said tubular bodies locate in said adjacent both zones to said intermediate zone, respectively, and an inside of each of said tubular bodies being isolated from said intermediate zone;
heat exchange being made through said tubular heat transferring members serving as heat transferring faces by supplying any one of the high temperature fluid and the low temperature fluid to any one of said adjacent both zones to said intermediate zone of said shell under a prescribed pressure, to cause said any one of the high temperature fluid and the low temperature fluid to pass through said tubular heat transferring members, and discharging said any one of the high temperature fluid and the low temperature fluid from the other of said adjacent both zones to said intermediate zone, while supplying the other of the high temperature fluid and the low temperature fluid to said intermediate zone from a side surface of said shell to cause it to flow between said tubular heat transferring members in a direction perpendicular to an axial direction of said tubular heat transferring members.
The heat exchanger of the present invention has a structure that the tubular heat transferring members serving as the heat transferring faces for making heat exchange are disposed in the box-shaped shell, any one of the high temperature fluid and the low temperature fluid passes through the inside of the tubular heat transferring members and the other of the high temperature fluid and the low temperature fluid passes through the region surrounding the tubular heat transferring members in a direction perpendicular to the above-mentioned any one of them so that the heat exchange can be made between the high temperature fluid and the low temperature fluid through the tubular heat transferring members. As a result, it is unnecessary to use any packing member in order to ensure the gap between the heat transferring faces. In addition, it is possible to ease restriction in pressure applied to fluid so that the fluid having a high temperature and a high pressure can be used. It is also possible to dispose a large number of heat transferring faces and increase the size thereof so as to improve the heat exchange efficiency. There is no occurrence of leakage at the packing members, thus improving remarkably the reliability. The opposite end portions of the tubular heat transferring members serve as an inlet to the inside of the tubular heat transferring members and an outlet therefrom and there is no opening formed in the intermediate portion of the tubular heat transferring members without wasting material in a blanking process for the tubular heat transferring members. It is therefore possible to provide economic effects and simplify the flow line of the fluid to reduce pressure loss.
In the heat exchanger of the present invention, the tubular heat transferring members may have on their surfaces a prescribed pattern of irregularity as an occasion demands. When the tubular heat transferring members have the prescribed pattern of irregularity in this manner in the present invention, it is possible to ensure a large area of the heat transferring faces. In addition, it is possible to cause evaporation or condensation more effectively when the heat exchanger is used as an evaporator or a condenser.
In the heat exchanger of the present invention, the tubular heat transferring members may have a porous inner surface as an occasion demands. When the tubular heat transferring members have a porous inner surface so as to increase, in the use of the heat exchanger as the evaporator, bubble generation cores of the fluid, which comes into contact with the inner surface of the tubular heat transferring members to be heated and to facilitate removal of the bubble generation cores, which have grown to a prescribed size, from the inner surface of the tubular heat transferring members, it is possible to facilitate the generation of bubbles so as to cause evaporation more effectively, thus improving the heat exchange efficiency. In addition, when the heat exchanger is used as the condenser, the porous inner surface of the tubular heat transferring members makes it possible to increase the area for the heat exchange, thus improving the condensation efficiency.